I'm really happy to know that you use my asset on one of your game! Yes I planning to make others packs. The next will be a pack with animated object like chest, door, torch.... And for the next probably faces for the characters on my character pack. For the next tiles pack it can be for Castle or dungeon, what do you prefer? Sorry to be long to make this assets, I'm working on my own game at the same time ^^'
Objects and faces, that's great! I didn't know you were going to make faces as well, so in the meantime I had to cut the face of the characters and use those, but it's not the same as with proper, more detailed faces ahah xD 
A castle or a dungeon, they both are useful... well of course it depends on what you want to do first, but thinking about my game, since you already made this cave pack, maybe a castle? My idea for this game is an interactive adventure with exploration and dialogue choices, so a castle to explore would be interesting.
Of course your game comes first, don't worry!